If a patient suffers a cardiac arrest for 30 seconds, he or she will suffer an acute sudden cardiac death. In addition, if cardiopulmonary resuscitation is not actively performed after 30 seconds of cardiac arrest, the patient may die clinically, so if cardiac arrest occurs, cardiopulmonary resuscitation must be performed immediately. To determine the patient’s consciousness, if the patient is unconscious and there is no fluctuation in the carotid artery on palpation, listen to the patient without heart sounds and no breathing or heartbeat, the patient is considered to be in cardiac arrest and should be given electric defibrillation or CPR at the same time. CPR should be performed in the CAB sequence, with chest compressions first, followed by opening the airway, and finally artificial respiration, until the defibrillator comes to the bedside to give the patient electric defibrillation.